1. Field of the Invention
This invention generally relates to an apparatus and method for image recognition, and more particularly to an apparatus and method for fingerprint recognition which projects interference fringes on a fingerprint to create a corresponding contour image thereof for image recognition.
2. Description of the Related Art
Conventional apparatus and method for fingerprint recognition is disclosed in U.S. Pat. No. 5,723,148 and shown in FIG. 1, entitled “Apparatus and method for electrically acquiring fingerprint images with low cost removable platen and separate image device”. The apparatus includes a housing 18 having an imaging aperture; a light source 22 for directing light 28 toward the imaging aperture; an imaging device 30 for receiving light reflected from a fingertip or other portion of a body visible through the imaging aperture and electronically sensing the image in the reflected light; and a low cost, easily replaceable, disposable platen 8 disposed in the imaging platen aperture and having a generally flat, thin configuration and having a first surface 26 upon which a portion of a body such as a fingertip is placed when the platen is in use and a second surface 12 which is generally parallel to the first surface 26 and which includes a plurality of projections comprising an optical structure, the projections being small enough to maintain the generally flat, thin configuration of the disposable platen 8 and comprised of material through which light can pass the plurality of projections of the optical structure having optical characteristics to prevent light rays originating at the light source 22 arriving at the second surface 12 from being reflected off the second surface 12 toward the imaging device 30 but instead causing the light rays 28 to enter the disposable platen 8 and travel through the disposable platen 8 so as to reach the first surface 26 without the need for guiding with the platen by total reflection, the configuration of the projections being such that most light rays refracted toward the second surface 12 from portions of the first surface 26 not in contact with flesh exit the first surface 26 and travel generally toward the imaging device 30, as shown in FIG. 3 of U.S. Pat. No. 5,723,148. In practical use, the fingerprint acquiring apparatus utilizes a cheap, replaceable and disposable platen so as to decrease the time and cost for maintaining the platen 8. However, since every individual has different distance interval between ridges of his fingerprint, the projections on the platen 8 of the second surface 12 have to be disposed differently in accordance with different individuals in order to improve the resolution of the acquired fingerprint image. Therefore, the apparatus still has the problem of high manufacturing complexity for the platen 8.
Accordingly, there is still a need to improve the structure of the fingerprint image acquiring apparatus in the art so as to increase the image quality of an acquired fingerprint image with minimized recognition apparatus.